wait without arguments always succeeds, with jobspec it returns the exit
code of that job.

Reading users from a file was deadlocking for a while now and I can't be
assed to fix it.

str_fail is 6 chars including \0.

The OTP is sent to all servers and authentication only succeeds if a
majority answers with OK. No communication between servers or their
backing DBs is necessary. Servers are re-synchronized after a (limited)
downtime by the usual lookahead range.

Will be used in other tests.

Just lines of "<username> <secret>" and comments beginning with '#'.

- install basic config
- create user and group
- create directory for DB
- install .service file

In the process, make the database connection object global because we
have to reconnect in order for the database settings to take effect and
thus have to reassign the variable.

The transaction_conflict test in its previous form would deadlock
because PostgreSQL locks tables/rows instead of aborting on every
conflict. The fix is to force a rollback by first reading and then
updating in both transactions, which would result in a lost update
otherwise.

Means we have to check if the user exists separately from checking the
offer.

Scanner aborts when lines are too long and is more flexible wrt.
line separators.